The research is concerned with the molecular analysis of the arrangement and regulation of genes in Drosophila melanogaster. More specifically, we are analyzing the histone genes and the genes belonging to regulatory hierarchies controlled by the steroid molting hormone, ecdysone. In regard to the histone genes, emphasis is placed on the higher order arrangement of the repeat units containing these genes. In the second category, we are investigating the genes responsible for the puffs in the polytene chromosomes of the larval salivary gland. Detailed analyses of the cloned genes that code for the glue protein and are transcribed in puffs that regress upon exposure to ecdysone will continue, with emphasis on the mechanisms by which ecdysone effects this regression. We are also devising new methods for the isolation of the genes transcribed in the early puffs that are induced by ecdysone, with the aim to determine how ecdysone causes this induction. We are also continuing our investigation of the multigene family expressed in larval and adults guts, having shown that different members of this family are expressed at different stages of development and in different parts of the gut. In addition to being subject to negative control by ecdysone, these genes may be positively controlled by juvenile hormone.